Wrought aluminum alloys are generally classified by series. There are currently eight different wrought alloy series, which are commonly referred to as 1 xxx-8xxx. The 1 xxx series aluminum alloys contain at least about 99.00 wt. % aluminum per Aluminum Association standards. The 2xxx-7xxx aluminum alloys do not have the same Al restriction, and are classified according to their main alloying element(s). The 2xxx aluminum alloys use copper, the 3xxx aluminum alloys use manganese, the 4xxx aluminum alloys use silicon, the 5xxx aluminum alloys use magnesium, the 6xxx aluminum alloys use magnesium and silicon, and the 7xxx aluminum alloys use zinc as their main alloying ingredient.
The 2xxx-7xxx are also generally split into two different categories: heat treatable and non-heat treatable. The non-heat treatable alloys are the 3xxx, 4xxx, and 5xxx aluminum alloys, whereas the heat treatable alloys are the 2xxx, 6xxx and 7xxx aluminum alloys. The 3xxx, 4xxx, and 5xxx aluminum alloys are classified as non-heat treatable because they cannot generally be appreciably strengthened by solution heat treatment. Instead, the 3xxx, 4xxx, and 5xxx aluminum alloys are usually strengthened by solid-solution, formation of second-phase microstructural constituents, dispersoid precipitates and/or strain hardening. Conversely, the 2xxx, 6xxx, and 7xxx aluminum alloys are considered heat treatable because they undergo significant strengthening when subjected to solution heat treatment and aging. The most prominent systems are Al—Cu—Mg, Al—Cu—Si, and Al—Cu—Mg—Si (all 2xxx aluminum alloys), Al—Mg—Si (a 6xxx aluminum alloy) and Al—Zn—Mg and Al—Zn—Mg—Cu (all 7xxx aluminum alloys).
High strength aluminum alloys, such as 5xxx series aluminum alloys (i.e., aluminum alloys containing magnesium as its main alloying ingredient), may be employed in various industries, such as in the military. However, it is difficult to improve the performance of one property of a 5xxx aluminum alloy (e.g., strength) without decreasing the performance of a related property (e.g., corrosion resistance).